Saudi authorities have arrested an activist who launched a campaign to challenge a ban on women driving in the conservative kingdom and posted a video on the internet of her behind the wheel, activists said. The YouTube video, posted on Thursday, has attracted more than 500,000 views and shows Manal Alsharif, who learned to drive in the US,driving her car in Khobar in the oil-producing Eastern Province.

"Police arrested her at 3am this morning," said Maha Taher, another activist who launched her own campaign for women driving four months ago to spread awareness of the issue.

An Eastern Province police spokesman declined to comment and an interior ministry spokesman was not immediately available for comment.

Saudi Arabia is an absolute monarchy that does not tolerate any form of dissent and applies an austere version of Sunni Islam, in which religious police patrol the streets to ensure public segregation between men and women.

Women are not allowed to drive and must have written approval from a designated guardian - a father, husband, brother or son - to leave the country, work or travel abroad.

The campaign Alsharif launched is aimed at teaching women to drive and encouraging them to start driving from 17 June, using foreign-issued licences.

While there is no written law that specifically bans women from driving, citizens must use locally issued licences which are not issued to women, making it effectively illegal for them to drive.

"When the police stopped her they told her she violated the 'norms'. There is no law that says women can't drive in Saudi Arabia and this arrest is unjust. She is a role model for a lot of people and the arrest will provoke her supporters. Now more women want to drive," Taher said.